I think it's important to know that the NOISH has recommended that hearing protection devices (HPD) that cannot be individually fitted ("fit tested") to the wearer be "de-rated" to more accurately reflect the level of protection they actually provide in real-world use. For example, if earplugs are removed by a shooter while outdoors at the range but not shooting, the NRR for the earplugs they were wearing drops for the day because of the time spent unprotected.

It's recommended that the NRR for muffs be reduced by 25%, for foam earplugs by 50% and for molded earplugs by 75%.

Next year, HPDs will no longer be rated by use of a single number but by a more accurate "range" method.